Armored military vehicles, such as tanks or the like are provided with a hatch opening closed by a hatch door in order that a crewman can open the hatch and partially rise through the opening for direct observation, weapon operation, etc. during maneuvers. However, when the hatch door is open, the vehicle interior is opened to inclement weather and vulnerable to poison gas and chemical attack. The present invention is a gas impermeable fabric, crewman's hood which accommodates the aforesaid direct observation by a crewman from an open hatch and seals off the hatch opening against inclement weather and chemical attack.